The present invention relates to a method and apparatus for reducing contamination in a plastic container, particular such a container that is employed for transporting semiconductor wafers in a semiconductor device manufacturing facility.
The ever present need to reduce particulate contamination in semiconductor device fabrication is well known. Within the clean room, semiconductor wafers are often transported between fabrication operations in closed, plastic containers. As the clean room is not completely devoid of particles, the containers assist in preventing some particles from reaching the wafers. However, the containers also introduce some contamination. For one thing, the containers may themselves have particles in them and, to prevent this, the containers need to be cleaned frequently. Typically, a detergent must be used to clean the internal surfaces of the container, the detergent being required to dislodge particles attracted to the container walls so that the particles may be flushed out. Organic molecules are also deposited on the interior surfaces of the containers used in 300 mm wafer processing. These containers are open to the machines processing the wafers with, among other things, photo-resist, and acquire deposits of organic compounds that must be cleaned with a solvent. Another form of contamination arises from outgassing of the plastic material. Organic molecules are constantly being released from the plastic and accumulate inside the closed container. These molecules deposit themselves on the wafers, further contaminating them.
To accomplish both types of cleaning has required separate washing facilities, for introducing both the detergent and the solvent. The use of the plastic container, though providing advantages, also exacts penalties in higher cost and increased manufacturing time. Accordingly, there is a need for a method and apparatus for reducing contamination in a plastic container that reduces or eliminates these penalties.